Support for legacy-format annotations

[dicksonlaw583]

As of the time of writing, only the "on":"URL#xywh=x,y,w,h" form of annotation has widespread support among viewers. Mirador should support creating annotations in this format via a configuration, for use cases where interoperability is a concern. When this configuration is on, only the rectangular tool should be allowed, with non-90-degree rotations disabled.

[mejackreed]

I think this could also be added to https://github.com/ProjectMirador/mirador-design so that @jvine and @ggeisler have some visibility to it